JP3001603U - Immersion tube used for vacuum degassing - Google Patents

Abstract

(57) [Abstract] [Purpose] The present invention is capable of preventing the occurrence of peeling and collapsing phenomenon of the inert gas discharging member, which is provided around the dip pipe, and discontinuity of the joint, and is also effective in Suffocation can be completely prevented. Further, it is possible to suppress the occurrence of peeling phenomenon, cracks, joint breakage, etc. of the refractory material forming the inner and outer cylinders of the dip tube, and prolong the life of the dip tube.
Further, it is possible to suppress the scattering of the slag and prevent a large number of the slag from adhering to the outer periphery and the flange of the non-immersed portion of the immersion pipe. [Constitution] According to the technical constitution of the present invention, in an immersion pipe which is immersed in molten steel for vacuum degassing treatment, an inert gas discharge member which is provided around the outer periphery of the immersion pipe is locked by a stopper. A vacuum degassing dip tube, and a structure in which a metal outer wall is provided around the bottom and lower end of the inert gas discharge member may be used.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a structure of a dip tube for vacuum degassing treatment, and more particularly to a structure capable of preventing collapse of an inert gas discharge member which is circumferentially arranged and arranged at a position including a region in contact with a molten steel surface of the dip tube.

[0002]

[Prior art]

 In recent years, quality requirements for steel materials are becoming more and more quality oriented, and not only the reduction of [P] [S] but also the reduction of ultrasonic flaws, the surface defects of steel based on high [N] content, so-called ground. Higher purity steel materials including reduction of [O] [H] [N] etc. are required for the purpose of improving pipe forming property by improving flaws and cleanliness, that is, bending workability and weldability of steel plate. ing. The development and advancement of the secondary refining method to meet this demand will improve the productivity of the entire steelmaking process and stabilize and improve the product quality, and the various characteristics and quality levels required for steel products. Is becoming more and more satisfied.

On the other hand, when [N] in the molten steel before RH vacuum degassing treatment is 30 PPM or less, particularly 25 PPM or less when lowering [N], various elements that are rate-determining factors of the de [N] reaction rate, that is, Not only does the reaction rate extremely decrease under the influence of surface-active elements such as [O] and [S], but also between the amorphous refractory and the seal metal that constitute the dip tube during the RH vacuum degassing process. A gap is created, or the refractories are connected by joints and cracks, and when the outside air enters the degassing equipment due to the difference in internal and external pressures, it is absorbed into the molten steel and lower [N] Was difficult to obtain.

Therefore, in order to suppress the invasion of the outside air and reduce [N] in the molten steel, for example, as in the method described in Japanese Patent Publication No. 2-19169, an iron core, which is a metal seal, is blown into a gas injection pipe. It is constructed as a double wall communicating with the outer wall, and a discharge hole is formed in the lower end of the double wall to discharge the inert gas such as Ar gas into the refractory, and the iron core and the inert gas are used to Methods to block intrusions have been proposed.

[0005]

[Problems to be solved by the device]

 At the same time, the structure of the immersion pipe in the RH-type vacuum degassing equipment is, for example, a horizontal brick that is divided into a plurality of studs and the like in the inner circumference of a cylindrical sealing metal object (hereinafter, Inner-wrapped brick) is lined to form an inner cylinder, and castable refractory and other irregularly shaped refractory are installed between the inner-wrapped brick and the seal metal and the outer circumference to form an outer cylinder. The dipping pipe used is usually one stage of an inert gas blowing pipe for recirculating Ar gas to introduce molten steel into the vacuum chamber, or about 4 to 30 pipes with upper and lower stages penetrating the inner and outer cylinders. Then, it is configured integrally. Further, in order to penetrate the inert gas blow-in pipe for recirculation, a through hole is also provided in the iron core, which is a metal seal, and after the inert gas blow-in pipe is passed through the through hole, it is welded or the like. It has been fixed beforehand. Therefore, when the iron core, which is a metal seal, is a double wall consisting of an inner pipe and an outer pipe, it is fixed by welding or other means to prevent outside air from entering the inner cylinder side through the through hole. Since it is necessary to make a close contact between the through hole and the inert gas blowing pipe for recirculation so that there is no gap between the through hole and the recirculating inert gas blowing pipe, the work becomes more complicated, and Ar gas or the like for the seal is used. There are also problems in production such as the need for 2 to 4 sealing gas injection tubes to inject the gas into the double wall consisting of the inner and outer cylinders, which requires more than double the work time and labor. When Ar gas is blown into the double wall, the entire iron core is cooled and the expansion difference between the iron core and the refractory cannot be absorbed, and the iron core and the refractory are repeatedly used. The phenomenon of peeling, joint breakage, cracks, etc. is further promoted, and the phenomenon that a so-called metal ingot is caused by the penetration of molten steel and inner winding bricks fall off is caused. In addition, since a discharge hole is formed at the lower end of the double wall to discharge an inert gas such as Ar gas into the refractory at the tip, the inert gas floats on the outer circumference of the dip pipe. By bubbling the surface of the molten steel, the slag scatters, and many scattered slags adhere to the outer peripheral surface and the flange of the non-immersed part of the immersion pipe.

[0006]

[Means for Solving the Problems]

 The inventors of the present invention have developed various types of immersion pipes for use in the vacuum degassing equipment of the present invention as a result of various studies and experiments to solve these problems. In a submerged pipe that is immersed in molten steel for vacuum degassing, the vacuum degassing is characterized in that the inert gas discharge member that is placed and arranged around the outer periphery of the submerged pipe is locked with a stopper. The treatment dip pipe may further have a structure in which a metal outer wall is provided on the outer periphery of the bottom and the lower end of the inert gas discharge member. With such a technical configuration, the dip pipe is provided around the outer periphery of the dip pipe. It is possible to prevent peeling and collapse phenomenon of the arranged inert gas discharge member, breakage of joints, etc. and to completely prevent nitrogen absorption into molten steel. Further, it is possible to suppress the occurrence of peeling phenomenon, cracks, joint breakage, etc. of the refractory material forming the inner and outer cylinders of the dip tube, and prolong the life of the dip tube. Further, it is possible to suppress the scattering of the slag and prevent a large number of the slag from adhering to the outer periphery of the non-immersed pipe and the flange.

The present invention will be further described below with reference to an embodiment shown in FIGS. 1 and 2.

The structure of, for example, a dip tube for vacuum degassing treatment according to the present invention is shown in FIG. 1 in a longitudinal sectional view, and in FIG. A cylindrical seal in which inner bricks 3 are divided into a plurality of pieces and arranged in parallel with the outer peripheral surface of the inner bricks 3 and the upper end is fixed to a flange 6 and a large number of studs 1 are planted on the outer circumference. For conventional RH equipment, where irregular shaped refractory 4 such as castable refractory 4 is arranged outside the metal 2 and a plurality of gas injection pipes 5 are arranged to form a two-layer integrated structure A porous refractory 7 exposed to the outside of the sealing metal 2 is provided around the immersion pipe, and an inert gas pool 9 is provided above the porous refractory 7, and the pool is provided with an inert gas supply pipe 8 Through an inert gas supply source (not shown) through the bottom of the porous refractory 7 and the outer periphery of the lower end. Is provided with a metal outer wall 10.

In the immersion pipe of the present invention, in addition to the immersion pipe for vacuum degassing treatment formed as described above, the upper position from the vicinity of the molten steel surface during processing of molten steel using the immersion pipe, preferably the lower end A porous refractory 7 is disposed outside the metal seal 2 which is located above the part that is partially immersed in the molten steel, and a gas supply pipe 8 for sealing is introduced, and the porous refractory 7 is introduced through a gas pool 9. Vacuum degassing treatment is performed while blowing an inert gas into the inside of the 7. The porous refractory 7 has, for example, an air permeability of 20 × 10 ⁻² × 60 × 10 ⁻² cm ³ · cm / cm ²・ Immersion for vacuum degassing, made of magnesia, corundum, corundum mullite, mullite corundum, etc. with a cmH ₂ O ・ sec level, and having a horizontal or vertical shape with a specified inner diameter and wall thickness. tube It is formed of a brick of a predetermined shape that is divided into a plurality of pieces in the circumferential direction according to the size, and the upper end is locked by a stopper 11.

In the present invention, as described above, cracks, joint breaks, etc. occur in the irregular refractory 4 and the inner brick 3 forming the immersion pipe, or the seal metal 2 and the irregular refractory 4 are formed. Is a mechanism that blocks the invasion of the outside air when the outer surface and the inner surface are in communication with each other due to the separation of the molten steel and the outer peripheral surface. The inert gas that is not harmful even if it remains in the molten steel such as Ar, CO, and CO ₂ gas from the inside of the porous refractory 7 surrounding the seal metal 2 at the upper position where the lower end part is partially immersed in the surface. By discharging at a pressure higher than the atmospheric pressure, the outer circumference of the upper part of the dip pipe not immersed in the molten steel is prevented from entering the outside air, and the outer wall 10 made of steel is formed around the bottom and the lower end of the porous refractory 7. By providing the It prevents the inert gas blown into the object 7 from flowing away to the inner peripheral surface side through the gap when the lower seal metal 2 and the amorphous refractory 4 are separated and a gap is created. is there.

The stopper 11 is made of, for example, ordinary steel such as rolled steel for general structure, or special steel such as stainless steel, and has predetermined wall thickness, length and width dimensions. As shown in the drawing, the L-shaped cross section is formed so that one end is filled with the outer periphery of the upper end of the porous refractory 7 and the other end is brought into contact with the lower surface of the flange 6 and fixed by means such as welding.

It should be noted that the gas pool is not limited to the shape shown in the figure, and its cross section should be semi-circular, L-shaped or inverted L-shaped so that the inert gas is evenly distributed and discharged to the outer periphery. You can Further, although the porous refractory is used as the inert gas discharging member, other mechanism or member that can make the outer peripheral portion of the immersion pipe on the molten steel bath surface into an inert gas atmosphere can be used. Further, although the fastener is also L-shaped in cross section, it can be trapezoidal, square, polygonal or semicircular in cross section (FIGS. 3a to 3d), and is not limited to the illustrated embodiment. .

Next, an example of the vacuum degassing treatment according to the present invention is performed in a 250T / chRH vacuum degassing facility by using the dipping pipe shown in FIGS. 1 and 2 and a conventional dipping pipe for RH equipment. As shown in FIG. 4, the apparatus of the present invention did not absorb nitrogen at all, and it was possible to reduce the amount of [N] in the molten steel to some extent. In addition, the entire sealing metal object is cooled by discharging the inert gas from inside the porous refractory located outside the sealing metal object above the molten steel surface of the immersion pipe during the molten steel treatment. In addition, the phenomenon of peeling from the refractory forming the inner and outer cylinders, cracks, and joint breakage were minimal. In addition, the outer wall made of steel and iron was provided around the bottom and the lower end of the porous refractory, and the perimeter of the porous refractory was locked by the metal fittings. The porous refractory that was exposed to the outside of the seal metal and was separated by the pressure of the inert gas to be discharged was separated and collapsed without flowing through to the inner peripheral surface side through the gap created by the separation. There was no loss of joints.

[0014]

[Effect of device]

 According to the mechanism of the present invention, cracks, joint breakage, etc. occur in the irregular refractory that forms the outer cylinder and the inner brick that forms the inner cylinder during operation, or there is a gap between it and the metal seal. Even if they are in communication with each other, it is possible to block the invasion of the outside air at the upper part of the dipping pipe that is not immersed in the molten steel, which is the entry port of the outside air, and as a result, the absorption of nitrogen into the molten steel is completely eliminated. Can be prevented. In addition, as in the method described in Japanese Examined Patent Publication No. 2-19169, the phenomenon of separation from the refractory material forming the inner and outer cylinders without the entire sealing metal article being cooled by the inert gas blown for sealing, or It is possible to suppress the occurrence of cracks, joint breaks, etc., and prevent the slag from scattering and adhering due to the bubbling of the molten steel surface, thus extending the life of the immersion pipe. it can. Furthermore, it is possible not only to prevent the inert gas blown into the porous refractory from flowing out to the inner peripheral surface side through the gap, but also to prevent the porous refractory from peeling and collapsing or severing locally. It is possible to prevent the discharge of the inert gas, and it is possible to enhance the effect of preventing the absorption of nitrogen with a smaller pressure of the inert gas.

[Submission date] April 15, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

In the immersion pipe of the present invention, in addition to the immersion pipe for vacuum degassing treatment formed as described above, the upper position from the vicinity of the molten steel surface during processing of molten steel using the immersion pipe, preferably the lower end A porous refractory 7 is disposed outside the metal seal 2 which is located above the part that is partially immersed in the molten steel, and a gas supply pipe 8 for sealing is introduced, and the porous refractory 7 is introduced through a gas pool 9. Vacuum degassing treatment is performed while blowing an inert gas into the inside of the 7, and the porous refractory 7 has, for example, an air permeability of 20 × 10 ⁻² to 60 × 10 ⁻² cm ³ · cm / cm ² · cm H ₂ O · sec approximately magnesia consists co random, corundum-mullite, mullite-corundum quality, etc., and lateral approaching shape or vertical approaching shape having a predetermined inner diameter and wall thickness, immersed for vacuum degassing process Are formed by bricks of a predetermined shape obtained by dividing a circumferential direction into a plurality fit of the size, it is engaged by the fastener 11 to the upper end.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an example of a dip tube of the mechanism of the present invention.

FIG. 2 is a transverse sectional view taken along the line AA of FIG.

FIG. 3 is a vertical sectional view showing various examples of a fastener used in the present invention.

FIG. 4 is a comparison diagram of changes in [N] amount between the mechanism of the present invention and the conventional system.

[Explanation of symbols]

 1 Irregular refractory locking metal 2 Seal metal 3 Inner brick 4 Indeterminate refractory 5 Inert gas blowing pipe 6 Flange 7 Porous refractory 8 Inert gas blowing pipe 9 Gas pool 10 Metal outer wall 11 Stopper

Claims (2)

[Scope of utility model registration request] 1. A submerged pipe for immersing in a molten steel for vacuum degassing, a stopper fitting surrounding an outer periphery of an upper end portion of an inert gas discharge member (7) which is provided around the outer peripheral portion of the submerged pipe. An immersion tube used for vacuum degassing, characterized in that it is locked in 11). 2. A submerged pipe for immersing in a molten steel for vacuum degassing, wherein a stopper fitting (11) surrounding the outer periphery of the upper end of an inert gas discharge member (7) arranged and arranged around the outer peripheral portion of the submerged pipe. ), And the inert gas discharge member (7)
An immersion pipe used for vacuum degassing treatment, characterized in that a metal outer wall (10) is provided on the bottom and the outer periphery of the lower end.